I made the central floral motif (see joint file) using a single open profile and a rail (outer edge of the floral motif) with rail revolve. I just realized that the result just outside the central part is distorted and I don't understand why? You need to look. at it from pretty close, at 10 and 11 o'clock the shape looks about ok but as you go away from this spot seems distorted.

sorry, I realised the apparent distorsions are just lighting effects. I made sure the profile and rail curve are orthogonal and that I can surface each of them with planar before using rail revolve, that why I didn't understand what was going on.